On 04/14/2011 12:44 AM, Dave Taht wrote:
In my travels this month I have been testing ECN enablement at homes and
hotels everywhere I go.
Until today, I was able to have the following settings for ECN on my laptop
everywhere I've been.
net.ipv4.tcp_ecn=1
#net.ipv6.tcp_ecn=0
net.ipv4.tcp_sack=1
net.ipv4.tcp_dsack=1
However, I got to visit Brian Clapper [1] (friend/co-author of gnugol)
tonight, and discovered that his fairly recently purchased router, a:
Etherfast Cable/DSL router Model BEFSR41
Firmware version 2.0.0.4
NOTE: Per the support web site for this device, firmware revision 2.00.4 is
the latest.
flat out refused to pass ECN enabled connection attempts (returning an ICMP
unreachable message)
He'd not noticed the problem because ubuntu 10.4 (at least, he also runs bsd)
has tcp_ecn=2, which so far as I know "tries" a ECN enabled connect then falls
back to not using it.
I'm bummed that such a recent router doesn't pass ECN, and will look into the
problem further in the morning.
So I think we must use tcp_ecn = 1 to TEST to make sure ECN is being passed,
and tcp_ecn=2 as the default recommendation.
Perhaps we can synthesize TCP streams to more directly test ECN capability in
the future somehow as part of our testing tools. Are there any tools that
synthesize TCP/ip we could use as a starting point?
[1] http://brizzled.clapper.org/
--
Brian Clapper, [email protected]
President & Principal Consultant: ArdenTex, Inc.
610.247.4395 (phone)
484.932.1270 (fax)
www.ardentex.com
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